LATE QUATERNARY PALEOCEANOGRAPHY IN THE FRAM STRAIT

Four sediment cores from the Fram Strait (78 degrees N) have been stud ied to reconstruct the paleoceanography of this major connection of th e Arctic Ocean to the world ocean. Back to oxygen isotope stage 5 (128 kyr ago) the stratigraphic interpretation of the cores is based on ox ygen isotope and accelerator mass spectrometry data; the identificatio n of oxygen isotope stage 6 is based on paleomagnetic and coccolith da ta. Parameters indicative for contrasting environmental conditions suc h as high input of ice-rafted detritus (IRD) or seasonally open waters display characteristic sequences by which the paleoce anography of th is region can be reconstructed for the last 180 kyr. The geographic se tting of Fram Strait and the sediment data indicate a permanent meridi onal circulation pattern throughout the last 180 kyr, as it is typical , for example, for the present-day circulation. Depending on the stren gth of advection, Atlantic waters appeared in Fram Strait as surface w aters, resulting in seasonally ice-free conditions, or as subsurface w ater masses, underlying polar waters perenially covered by ice. Sustai ned periods of seasonally ice-free waters were largely restricted to i nterglacial stages 5.5, 5.1, and the Holocene. However, a few short ev ents characterized by seasonally ice-free conditions at 78 degrees N a re recorded during glacial stages as well, for example, stage 6, late stage 3, and stage 2 (''Nordway'' events). These events provide for su pply of moisture, and therefore they are closely related to the histor y of the European Arctic ice sheets. Strong input of IRD, reflecting s evere glaciations on surrounding landmasses, occurred during most of s tage 6, in early stage 3, and during stage 2. Variations in IRD input allow differentiation between three major source areas: (1) Svalbard/B arents Sea during major glacier advances in stages 2 to 5; (2) most li kely Siberia during stage 6; and (3) Fennoscandia during the short eve nts in glacial periods marked by seasonal open waters. Thus the circul ation pattern in the Fram Strait remained rather stable throughout the last 180 kyr, while variations in the sediment composition are mainly due to the intensity of Atlantic water advection and to the prevailin g IRD input pathway.